Our long-term goal is to determine the biochemical identity of transfer factor (TF) and to delineate its mechanism of action by both in vivo and in vitro methods. We continue to investigate reproducible in vitro assays of TF activity and potential animal models of TF activity. In these studies we plan to continue our studies on: 1) effects of leukocyte dialysates containing TF on various in vitro correlates of cellular immunity including lymphocyte blastogenesis, lymphokine production and T-lymphocyte-sheep red cell rosette formation; 2) a system for the in vitro production of TF directed against specific histocompatibility antigens; 3) the biochemical purification of components of leukocyte dialysates and the characterization of the active materials; 4) the production of antisera against leukocyte dialysates and the study of the specificities of these antisera with the ultimate goal of developing a radioimmunoassay for TF; 5) the potential role of the mouse as a laboratory animal in which to study the production and expression of TF.